easter_date

Guillaume Dufrene (2013-03-30 08:13:56)

I found a problem with holidays timestamp computation and daylight saving time.
An article about it at http://goo.gl/76t31 (in french only, sorry).
In summary, this year (2013) easter begins before adding an hour for daylight saving time (occured sunday at 3:00). It means that if you do $easter + X, where x is a number of seconds equivalent to one day, 39 days or 50 days, the result is not equals to a midnight timestamp...
Here a function to check if a midnight timestamp is equals to an holiday :
function isHoliday( $ts ) {
// Licence : Creative Commons (BY)
// By Webpulser - http://goo.gl/76t31
$fixed_holidays = array( ’01-01′, ’01-05′, ’08-05′, ’14-07′, ’15-08′, ’11-11′, ’25-12′ );
$format = ‘d-m’;
$dm = date($format, $ts);
if ( in_array($dm, $fixed_holidays) ) return true;
$easter = easter_date( date(‘Y’, $ts) );
if ( date($format, $easter + 86400) == $dm ) return true;
if ( date($format, $easter + 3369600) == $dm ) return true;
if ( date($format, $easter + 4320000) == $dm ) return true;
return false;
}
feel free to use / modify.

luca at musician dot org (2012-05-03 15:19:01)

Due to range limitations of core functions such as easter_date(), mktime(), strtotime(), I wrote this function to get the Easter Day in string format yyyy-mm-dd.
function myEaster($year)
{
/*Warning: easter_date(): This function is only valid for years between 1970 and 2037
* The easter_days() function can be used instead of easter_date() to calculate Easter for years which fall outside the range.
*/
//The next line would do the work if there were no limitations:
//return date("Y-m-d",easter_date($year));
/*Outside range (1970,2037) they advise to use easter_days().
* Unfortunately, when you have to create a date object as 21-03-yyyy to which add easter_days(), then obtain Easter,
* functions like strtotime(), DateTime::createFromFormat() will fail. (return value is 01-01-1970)
*/
$march21=date("$year-03-21");
$days=easter_days($year);
if($year<=2037)
//The next line would do the work if strtotime() wasn't affected by same limitations. But, the if..else is required to handle all years.
$date = date("Y-m-d",strtotime(date("Y-m-d", strtotime($march21)) . " +$days day"));
else
{
if($days<=10){
$day=str_pad(21+$days, 2, '0', STR_PAD_LEFT);
$date=date("$year-03-$day");
}
else
{
$day=str_pad($days-10, 2, '0', STR_PAD_LEFT);
$date=date("$year-04-$day");
}
}
return $date;
}

py dot lebecq at gmail dot com (2010-03-11 07:44:45)

I recently had to write a function that allows me to know if today is a holiday.

And in France, we have some holidays which depends on the easter date. Maybe this will be helpful to someone.

Just modify in the $holidays array the actual holidays dates of your country.

<?php
/**
 * This function returns an array of timestamp corresponding to french holidays
 */
protected static function getHolidays($year = null)
{
  if ($year === null)
  {
    $year = intval(date('Y'));
  }
    
  $easterDate  = easter_date($year);
  $easterDay   = date('j', $easterDate);
  $easterMonth = date('n', $easterDate);
  $easterYear   = date('Y', $easterDate);

  $holidays = array(
    // These days have a fixed date
    mktime(0, 0, 0, 1,  1,  $year),  // 1er janvier
    mktime(0, 0, 0, 5,  1,  $year),  // Fête du travail
    mktime(0, 0, 0, 5,  8,  $year),  // Victoire des alliés
    mktime(0, 0, 0, 7,  14, $year),  // Fête nationale
    mktime(0, 0, 0, 8,  15, $year),  // Assomption
    mktime(0, 0, 0, 11, 1,  $year),  // Toussaint
    mktime(0, 0, 0, 11, 11, $year),  // Armistice
    mktime(0, 0, 0, 12, 25, $year),  // Noel

    // These days have a date depending on easter
    mktime(0, 0, 0, $easterMonth, $easterDay + 2,  $easterYear),
    mktime(0, 0, 0, $easterMonth, $easterDay + 40, $easterYear),
    mktime(0, 0, 0, $easterMonth, $easterDay + 50, $easterYear),
  );

  sort($holidays);
  
  return $holidays;
}
?>

peter dot burden at gmail dot com (2010-01-28 16:55:34)

In 5.3.1 easter_date() returns GMT of start of Easter Day in UK allowing
for UK Summer Time. If you are in another time zone you need to 
calculate offsets.
<?php
        $e1 = easter_date(2008);
        $e2 = easter_date(2009);
        echo "Timestamps " . $e1 . " " . $e2 . "\n";

        //      Timestamps 1206230400 1239490800

        echo "Days between Easter 2008 Easter 2009 = " . ($e2-$e1)/86400 . "\n";

        //      Days between Easter 2008 Easter 2009 = 384.958333333 - i.e. 384 days 23 hours

        date_default_timezone_set("Europe/London");
        echo date( " l, jS F Y H:i TO",$e1) . "\n";
        echo date( " l, jS F Y H:i TO",$e2) . "\n";

        //      Sunday, 23rd March 2008 00:00 GMT+0000
        //      Sunday, 12th April 2009 00:00 BST+0100

        date_default_timezone_set("America/New_York");
        echo date( " l, jS F Y H:i TO",$e1) . "\n";
        echo date( " l, jS F Y H:i TO",$e2) . "\n";

        //      Saturday, 22nd March 2008 20:00 EDT-0400
        //      Saturday, 11th April 2009 19:00 EDT-0400
        //      Daylight saving time in effect - New York 4 hours behind GMT
?>

maxie (2008-06-12 01:36:46)

To compute the correct Easter date for Eastern Orthodox Churches I made a function based on the Meeus Julian algorithm:

<?php
function orthodox_eastern($year) {
    $a = $year % 4;
    $b = $year % 7;
    $c = $year % 19;
    $d = (19 * $c + 15) % 30;
    $e = (2 * $a + 4 * $b - $d + 34) % 7;
    $month = floor(($d + $e + 114) / 31);
    $day = (($d + $e + 114) % 31) + 1;
    
    $de = mktime(0, 0, 0, $month, $day + 13, $year);
    
    return $de;
}
?>

nigelf at esp dot co dot uk (2008-01-28 03:50:23)

v5.2.1 - There is a known bug with easter_date() that can return incorrect dates for some years:

<?php
// 2008 OK
echo date("D d M Y", easter_date(2008));  // Sun 23 Mar 2008

// 2009 returns Saturday
echo date("D d M Y", easter_date(2009));  // Sat 11 Apr 2009
?>


However easter_days() works correctly:

<?php
echo date("D d M Y", strtotime("2009-03-21 +".easter_days(2009)." days"));  // Sun 12 Apr 2009
?>

It is apparently related to timezone settings.

(2006-08-14 07:46:15)

I made the function like this ... works fine !

<?php
function ostern
{
    $maerz21=date('z',mktime(0,0,0,3,21,$jb));

    $d=((15 + $jb/100 - $jb/400 - (8 * $jb/100 + 13) / 25)%30 + 19 * ($jb%19))%30;

    if ($d==29)
    {
        $D=28;
    }
    elseif($d==28 && ($jb%17)>=11)
    {
        $D=27;
    }
    else $D=$d;    

    $e=(2 * ($jb%4) + 4 *($jb%7) + 6 * $D + (6 + $jb/100 - $jb/400 - 2)%7)%7;

    $ostersonntag=$e+$D+1+$maerz21;
    return $ostersonntag;
}
?>

phpuser (2004-11-08 08:17:16)

The algorithm from Bigtree is correct if you add some (int) cast
<?php 
   function easter_date ($Year) { 
   
       /* 
       G is the Golden Number-1 
       H is 23-Epact (modulo 30) 
       I is the number of days from 21 March to the Paschal full moon 
       J is the weekday for the Paschal full moon (0=Sunday, 
         1=Monday, etc.) 
       L is the number of days from 21 March to the Sunday on or before 
         the Paschal full moon (a number between -6 and 28) 
       */ 
       

         $G = $Year % 19; 
         $C = (int)($Year / 100); 
         $H = (int)($C - (int)($C / 4) - (int)((8*$C+13) / 25) + 19*$G + 15) % 30; 
         $I = (int)$H - (int)($H / 28)*(1 - (int)($H / 28)*(int)(29 / ($H + 1))*((int)(21 - $G) / 11)); 
         $J = ($Year + (int)($Year/4) + $I + 2 - $C + (int)($C/4)) % 7; 
         $L = $I - $J; 
         $m = 3 + (int)(($L + 40) / 44); 
         $d = $L + 28 - 31 * ((int)($m / 4)); 
         $y = $Year; 
         $E = mktime(0,0,0, $m, $d, $y); 

         return $E; 

   } 
?>